The present invention relates to molten slag runners for blast-furnace plants, and more particularly the invention relates to a molten slag runner comprising forced-cooling copper or copper alloy trough elements and designed so that the molten slag flowing from a blast furnace and separated from the molten iron is introduced into a slag pit, such as, a dry pit or water pit, water jet spray unit for the manufacture of granulated slag or molten slag ladle.
In the past, the prior art molten slag runners for blast-furnace plants have generally consisted of a trough constructed by stamping formless refractory material. The runner of this type is disadvantageous in that the molten slag sticks to the inner wall of the trough made from refractory material thus causing damage or wear of the coating laid over the refractory material, and particularly such damage or wear will be particularly great in the bent portions as well as the terminal end portions of the runner where the effect of the kinetic energy of the molten slag stream is so great and the heat load is also increased greatly. While such damaged or worn-out portions must be repaired by stamping formless refractory material, such repair work must be carried out in a high temperature atmosphere where not only some danger is involved but also the efficiency of the work is low. These deficiencies have come to be recognized as serious problems in the light of the recent tendency toward larger blast furnaces with the resulting increase in the flow rate of slag in the runners, and there has existed the need to overcome these deficiencies. Another disadvantage of the slag runner consisting of a trough made of refractory material is that it is difficult to subject the molten slag to force cooling thus causing difficulties in reducing the temperature of the molten slag to a desired level and processing the slag to produce a hard granulated slag product.
In other words, as one of the specific uses of the molten slag from a blast furnace, it is well known in the art to convert the molten slag into a hard granulated slag product having a large weight per unit volume and to use it in slag cements or concrete units as a replacement for sand. In the manufacture of such granulated slag by a granulation method employing water, the most effective way of increasing the weight per unit volume and the hardness of the granulated slag is to decrease the temperature of the raw material or molten slag and then effect the granulation. However, where the molten slag from a blast furnace is directly continuously subjected to water granulation, in the case of a molten slag runner consisting of a trough made of refractory material, it is impossible to regulate and control so that the temperature of the molten slag is forcibly reduced to a desired level prior to the granulation. With this type of molten slag runner consisting of a trough made of refractory material, the temperature of the molten slag outflowing from the runner end is usually relatively high ranging from 1,470.degree. to 1,520.degree. C. with the result that even if the pressure and quantity of water jets for the water granulation of the molten slag are increased, the maximum possible weight per unit volume of the resulting granulated slag will be on the order of 1.3 Kg/l and it will be extremely difficult to produce stably a product having a greater value of Kg/l.
While a solid addition agent may be added as a cooling agent to the molten slag as a method of cooling the molten slag prior to the granulation, it is still difficult for this method to ensure a continuous temperature control for the continuous stream of the molten slag, and moreover additional provisions for introducing such cooling agent must be made above the slag runner thus upsetting the arrangement of the units around the blast furnace. Further, while the installation of a cooling hose inside the refractory trough may be proposed as a means of cooling the molten slag, inferior heat conduction of the refractory material constituting the trough results in poor response of the control for cooling and its use in practical applications is extremely difficult.